Preparation,homogeneity and stability studies of a candidate LRM for Se speciation

A laboratory reference material (LRM) was prepared from Brazil nuts (Bertholletia excelsa) for quality control (QC) purposes of selenium speciation. The preparation of this LRM led through the usual operation steps applied during routine reference material production from biota samples-preparation of the raw material, homogenisation, storage design, checking of homogeneity, microbiological status and possible irradiation effects, and monitoring the species stability vs time at different storage temperatures. The selenium speciation studies to check species stability were carried out on a HPLC-UV-HG-AFS measurement set-up. Special attention was paid to the correct identification of selenium species by applying independent HPLC separation techniques (ion-pairing and anion-exchange chromatography). The concentration of selenomethionine (SeMet) and total Se content were quantified (79.9 microg g(-1) (calculated as Se) and 82.9 microg g(-1), respectively). The homogeneity and stability of this candidate reference material passed the relevant tests recommended by Bureau Communautaire de Référence (BCR).     

Synthesis and further transformations of 8-chloro-3,4-dihydroisoquinoline

Two procedures for the synthesis of barely accessible 8-chloro-3,4-dihydroisoquinoline were investigated. The first approach is based on a directed ortho-lithiation of N-pivaloyl meta-chlorophenylethylamine, followed by formylation and subsequent ring closure under acidic conditions. In the second, more advantageous variant, the N-hydroxyethyl ortho-chlorobenzylamine intermediate undergoes a Friedel-Crafts reaction, and the resulting tetrahydro derivative is oxidized with N-bromosuccinimide. The 8-chloro-3,4-dihydroisoquinoline key intermediate is then applied in Suzuki reactions to give various 8-aryl-3,4-dihydroisoquinolines, which are finally treated with alkyl or aryllithiums to give 1-substituted 8-aryl-1,2,3,4-tetrahydroisoquinolines. These novel 1,2,3,4-tetrahydroisoquinoline derivatives can be used as building blocks in the synthesis of potential drug candidates.     

Fission products from the damaged Fukushima reactor observed in Hungary

Fission products, especially ¹³¹I, ¹³⁴Cs and ¹³⁷Cs, from the damaged Fukushima Dai-ichi nuclear power plant (NPP) were detected in many places worldwide shortly after the accident caused by natural disaster. To observe the spatial and temporal variation of these isotopes in Hungary, aerosol samples were collected at five locations from late March to early May 2011: Institute of Nuclear Research, Hungarian Academy of Sciences (ATOMKI, Debrecen, East Hungary), Paks NPP (Paks, South-Central Hungary) as well as at the vicinity of Aggtelek (Northeast Hungary), Tapolca (West Hungary) and Bátaapáti (Southwest Hungary) settlements. In addition to the aerosol samples, dry/wet fallout samples were collected at ATOMKI, and airborne elemental iodine and organic iodide samples were collected at Paks NPP. The peak in the activity concentration of airborne ¹³¹I was observed around 30 March (1–3 mBq m^?3 both in aerosol samples and gaseous iodine traps) with a slow decline afterwards. Aerosol samples of several hundred cubic metres of air showed ¹³⁴Cs and ¹³⁷Cs in detectable amounts along with ¹³¹I. The decay-corrected inventory of ¹³¹I fallout at ATOMKI was 2.1±0.1 Bq m^?2 at maximum in the observation period. Dose-rate contribution calculations show that the radiological impact of this event at Hungarian locations was of no considerable concern.     

Nanofiltration and electrodialysis: alternatives in heavy metal containing high salinity process water treatment

Desalination is priority in process water treatment and several different technologies can be applied to minimize the total salinity of water. Our aim was to study desalination and simultaneous elimination of heavy metal residues from process waters. Nanofiltration (NF) and electrodialysis (ED) treatment technologies were applied for high salinity model solutions and high salinity, heavy metal containing real process waters originating from electroplating industry. Efficiencies of two technologies were compared in respect to salt and heavy metal removal both for model solutions (NaCl and Na₂SO₄) and three real process water samples. Initial concentrations of model solutions chosen accordingly the most common process water salt composition. Both technologies showed similar efficiency of heavy metal (Ni²⁺ and Cu²⁺) removal; however, they provide different demineralization rates, rejection, and extraction percentage for sodium and chloride ions. ED experiments of model solutions showed complete desalination after 1 h operating time at 6 V applied voltage; on the other hand, the increasing conductivities of NF permeates verified the selectivity of NF membrane, therefore, representing partial desalination. These phenomena were confirmed by demineralisation rate values as well (NF: for NaCl: 41.5–66.6%, for Na₂SO₄: > 96.6%; ED: both for NaCl and Na₂SO₄ > 98%). Significantly. higher demineralisation rates were achieved by ED (37.3–99.2%) than NF (20.2–62.3%) during the treatment of real process waters. We successfully demonstrated that ED is more efficient for simultaneous salt and heavy metal removal for process waters originating of electroplating industry.     

Small Edge Sets Meeting all Triangles of a Graph

It was conjectured in 1981 by the third author that if a graph G does not contain more than t pairwise edge-disjoint triangles, then there exists a set of at most 2t edges that shares an edge with each triangle of G. In this paper, we prove this conjecture for odd-wheel-free graphs and for ‘triangle-3-colorable’ graphs, where the latter property means that the edges of the graph can be colored with three colors in such a way that each triangle receives three distinct colors on its edges. Among the consequences we obtain that the conjecture holds for every graph with chromatic number at most four. Also, two subclasses of K ₄-free graphs are identified, in which the maximum number of pairwise edge-disjoint triangles is equal to the minimum number of edges covering all triangles. In addition, we prove that the recognition problem of triangle-3-colorable graphs is intractable.     

Color-bounded hypergraphs, I: General results

The concept of color-bounded hypergraph is introduced here. It is a hypergraph (set system) with vertex set X and edge set E={E₁,…,E_m}, where each edge E_i is associated with two integers s_i and t_i such that 1≤s_i≤t_i≤|E_i|. A vertex coloring φ:X→N is considered to be feasible if the number of colors occurring in E_i satisfies s_i≤|φ(E_i)|≤t_i, for all i≤m.Color-bounded hypergraphs generalize the concept of ‘mixed hypergraphs’ introduced by Voloshin [V. Voloshin, The mixed hypergraphs, Computer Science Journal of Moldova 1 (1993) 45-52], and a recent model studied by Drgas-Burchardt and ?azuka [E. Drgas-Burchardt, E. ?azuka, On chromatic polynomials of hypergraphs, Applied Mathematics Letters 20 (12) (2007) 1250-1254] where only lower bounds s_i were considered.We discuss the similarities and differences between our general model and the more particular earlier ones. An important issue is the chromatic spectrum-strongly related to the chromatic polynomial-which is the sequence whose kth element is the number of allowed colorings with precisely k colors (disregarding color permutations). Problems concerning algorithmic complexity are also considered.